JP3963355B2

JP3963355B2 - Flame detector

Info

Publication number: JP3963355B2
Application number: JP2002125347A
Authority: JP
Inventors: 秀成松熊
Original assignee: Hochiki Corp
Current assignee: Hochiki Corp
Priority date: 2002-04-26
Filing date: 2002-04-26
Publication date: 2007-08-22
Anticipated expiration: 2022-04-26
Also published as: JP2003317162A

Description

【０００１】
【発明の属する技術分野】
本発明は、炎検出装置に関し、詳しくは、炎の発光を利用して火災に伴う炎の検出を行う炎検出装置に関する。
【０００２】
【従来の技術】
炎から放射する光には可視光、紫外光及び赤外光といった様々な波長域の光が含まれているが、特に３〜５μｍ程度の赤外光には、燃焼時に生成されるＣＯ₂の共鳴放射と呼ばれる特定波長域（４．３μｍ付近の波長域）の光が含まれ、しかも、可視光のように周囲の光の影響を受けにくいため、この特定波長域を中心とした所定帯域の赤外エネルギーをセンサで検出し、所定レベル以上のエネルギーが検出されたときに火災に伴う炎の発生を判定するようにした炎検出装置が知られている。
【０００３】
さらに、炎の発光エネルギーは、低い周波数（一般に数Ｈｚ程度）の帯域を中心とした揺らぎ（以下「揺らぎ信号成分」という）を持つことも知られており、上述のエネルギー強度の判定に加えて、時系列信号出力の周波数解析等によって求めた周波数特性を元に太陽光や照明光などの外乱光による誤判定を排除して検出精度の向上を図った炎検出装置も知られている。
【０００４】
図１２は、炎検出装置と赤外エネルギー放射体（以下「被検物」という）との関係図であり、１は炎検出装置の内部に設けられた検知素子、２は被検物である。検知素子１は受光面１ａに到達した被検物２からの赤外エネルギーを電気信号に変換して出力する例えば焦電型の赤外線センサである。なお、受光面１ａの前面に特定波長域の光を通過させるための光学波長フィルタを装着しているが、図では省略してある。
【０００５】
検知素子１の出力信号レベルは、検知素子１と被検物２との間の距離Ｒや赤外エネルギーの受光面への入射角θ（θは検知素子１の受光面の法線３とのなす角度）によって変化する。例えば、Ｒが大きくなると出力信号レベルは減少し、また、θが大きくなっても出力信号レベルは減少する。
【０００６】
今、被検物２を規定の火炎モデルにするとともに、Ｒやθを様々に変化させながら検知素子１の出力信号レベルを平面図表上にプロットし、炎の検知が可能な最小の出力信号レベルのプロット点を結ぶことにより、炎検出装置の検知エリアを把握できる。
【０００７】
図１３は、検知エリアを示す図である。図において、４は炎検出装置、５は不図示の受光面の法線、６は炎の検知が可能な最小の出力信号レベルのプロット点を結んだ線であり、この線６の内側が検知エリア（以下、線６を検知エリアという）になる。但し、図では炎検出装置４の近くにある無効エリア（出力信号レベルが大きすぎて正確な炎の検知を行えないエリア）を省略している。
【０００８】
検知エリア６は、炎検出装置４（の検知素子）の受光点Ｐから扇状に広がるとともに、その先で曲線を描いて閉じた形になっており、曲線上の任意点ｘと受光点Ｐとを結ぶ直線の長さＬは、炎の検知が可能な最小の出力信号レベルに対応する上記距離Ｒに相当する。また、曲線上の任意点ｘと受光点Ｐとを結ぶ直線と法線５とのなす角φは、同じく炎の検知が可能な最小の出力信号レベルに対応する上記入射角θに相当する。
【０００９】
図示の検知エリア６において、炎の検知が可能な距離Ｒの最大地点はθが最小（θ＝０）となる法線４上の点ｙにある。すなわち、検知エリア６の受光点Ｐから最も遠い部分は点ｙの付近にある。
【００１０】
このような形状の検知エリア６を有する炎検出装置４を、実際の火災監視対象に適用する場合は、図１４に示すように、監視エリア８の全体が検知エリア６に完全に収まるように炎検出装置４の設置位置等の調節を行う。これにより、監視エリア８の全体を漏れなく監視することができる。
【００１１】
【発明が解決しようとする課題】
しかしながら、上記従来の炎検出装置にあっては、検知エリア６の形状、特に最遠部の形状が曲線状になっているため、監視エリアの一般的な形状（矩形状）と一致せず、監視エリア８の外側に無用な検知エリア９が広がっていた。
【００１２】
このため、例えば、図１５に示すように、監視エリア８の境界部分に窓のような開口部１０がある場合には、太陽や外灯などの外部光源１１からの光が開口部１０を通して入り込み、炎検出装置４で受光される結果、誤警報を発することがあるという問題点があった。
【００１３】
したがって、本発明が解決しようとする課題は、検知エリアの形を変更して、対象となる監視エリアの外側の無用な検知エリアを縮小することにある。
【００１４】
【課題を解決するための手段】
請求項１記載の発明は、透光部材を介して入射する赤外エネルギーを電気信号に変換して出力する検知素子を備えた、監視領域における火災を検出する炎検出装置において、前記透光部材に複数の領域を設け、前記検知素子の検知エリアが前記監視領域を完全に含み且つ監視領域の形状に検知エリアが沿うように、前記透光部材の各領域の前記赤外線エネルギーに対応する透過率に差を持たせたことを特徴とする。
請求項２記載の発明は、請求項１記載の発明において、表面荒さの異なるすりガラス加工によって前記透過率の差を持たせたことを特徴とする。
請求項３記載の発明は、請求項２記載の発明において、すりガラス加工面を検知素子に対向する面としたことを特徴とする。
請求項４記載の発明は、請求項１記載の発明において、透過波長帯域幅の異なる光学波長フィルタを用いて前記透過率の差を持たせたことを特徴とする。
請求項５記載の発明は、請求項１記載の発明において、前記領域は、同心円状の複数の領域であることを特徴とする。
請求項６記載の発明は、請求項１記載の発明において、前記領域は、同心円状の領域と楕円状の領域を含むことを特徴とする。
請求項７記載の発明は、請求項１記載の発明において、前記領域は、帯状の領域であることを特徴とする。
請求項８記載の発明は、請求項７記載の発明において、前記帯状の領域の少なくとも一つを更に透過率の異なる複数の領域に分割することを特徴とする。
請求項９記載の発明は、請求項１記載の発明において、前記透光部材の中央部に位置する領域の透過率が最低、前記透光部材の周縁部に位置する領域の透過率が最大となるように設定することを特徴とする。
請求項１０記載の発明は、請求項１記載の発明において、前記透光部材の直径方向に沿って各領域の透過率が増大又は減少変化することを特徴とする。
請求項１１記載の発明は、透光部材を介して入射する赤外エネルギーを電気信号に変換して出力する検知素子を備えた、監視領域における火災を検出する炎検出装置において、前記検知素子を二次元平面に複数個配列し、該炎検知装置の検知エリアが前記監視領域を完全に含み且つ監視領域の形状に検知エリアが沿うように、中央付近の検知素子の検知面サイズを周囲の検知素子の検知面サイズより小さくすることを特徴とする。
【００１５】
【発明の実施形態】
以下、図面を参照して本発明の実施形態を詳細に説明する。
【００１６】
図１は、炎検出装置の構造図である。炎検出装置２０は、薄型円筒状のケース２１と、このケース２１の内部に収められたセンサパッケージ２２とを備えており、ケース２１の一端面にはめ込まれた透光部材２３を介して外部の赤外エネルギーを取り込み、センサパッケージ２２の光学波長フィルタ２４でフィルタリングされた特定波長域の信号光を検知素子２５で受光して電気信号に変換し、不図示の炎検出部に出力する。
【００１７】
なお、光学波長フィルタ２４は、例えば、燃焼時に生成されるＣＯ₂の共鳴放射と呼ばれる４．３μｍ付近の波長域を含む波長帯の透過特性を持つものであり、また、検知素子２５は、例えば、焦電型の赤外線センサであるが、これに限定されない。要は、炎の発光を利用して火災に伴う炎の検出を行う炎検出装置に必要な検知特性を持つものであればよい。
【００１８】
図示の炎検出装置２０の検知視野角θＴは、検知素子２５の受光面（光学波長フィルタ２４に対向する面）の端と透光部材２３の端とを結んだ線２６、２７の開き角度で与えられ、この角度θＴは、図１３の検知エリア６における炎検出装置４（の検知素子）の受光点Ｐから扇状に広がる角度に相当する。
【００１９】
本実施形態の特徴的な事項は、専ら透光部材２３の構造にある。すなわち、透光部材２３の一の役割は、従来技術の透光部材と同様に、ケース２１と一体になって雨滴や埃などからセンサパッケージ２２を保護する点にあるが、本実施形態では、さらに検知視野角θＴの範囲内の入射光に対して入射角に応じた異なる透過率を与えるという二の役割を持つ点で従来技術と相違する。
【００２０】
図２は、本実施形態の透光部材２３の平面図である。略円形に成形された薄板状の透光部材２３は、図示の例では三つの同心円領域２３ａ、２３ｂ及び２３ｃを有しており、各領域の透過率をそれぞれＴａ、Ｔｂ、Ｔｃとすると、Ｔａ＞Ｔｂ＞Ｔｃの関係にある。但し、Ｔａはほぼ１００％またはできるだけ１００％に近い値である。ここで、透過率（Ｔｒａｎｓｍｉｔｔａｎｃｅ）とは、物質層または異なる２媒質の境界面を通して波動が透過するとき、入射波に対する透過波の強度の比（一般に％で表す）をいう。例えば、透過率が１００％のときは入射波の強度と透過波の強度が相等しく（透過損失がゼロ）、また、透過率が０％のときは入射波のすべてが透過中に失われて透過波の強度がゼロになる。
【００２１】
図３は、図２の透光部材２３を用いた場合の検知素子２５の信号強度を示す図である。３０ａ〜３０ｃの扇状図形は、透光部材２３の各領域２３ａ〜２３ｃに対応する信号を表し、扇の根元から先端までの長さで信号強度を模式化している。すなわち、Ｔａ＞Ｔｂ＞Ｔｃであるから、透過率Ｔａを有する領域２３ａの透過波強度が最大となり、透過率Ｔｂを有する領域２３ｂの透過波強度がそれに次ぎ、透過率Ｔｃを有する領域２３ｃの透過波強度が最小となっている。
【００２２】
三種類の扇状図形３０ａ〜３０ｃの長さの差は、透光部材２３の各領域２３ａ〜２３ｃの透過率の差に対応し、例えば、Ｔａ＝９０％、Ｔｂ＝６０％、Ｔｃ＝３０％とすると、Ｔａ、Ｔｂ及びＴｃの各々の透過率差は３０％であるから、検知素子２５の受光特性を無視すれば、三種類の扇状図形３０ａ〜３０ｃの長さの差は、各々３０％相当になる。
【００２３】
図４は、上記の透光部材２３を備えた炎検出装置２０の検知エリア３１を示す図である。図示の検知エリア３１は、三種類のエリア３１ａ〜３１ｃを合成したものであり、第一のエリア３１ａは上記扇状図形３０ａに対応し、第二のエリア３１ｂは上記扇状図形３０ｂに対応し、第三のエリア３１ｃは上記扇状図形３０ｃに対応する。
【００２４】
今、透光部材２３の領域２３ａの透過率Ｔａを従来の透光部材の透過率と同じ値とすれば、従来の炎検出装置の検知エリア６（以下「従来検知エリア」という）は破線の範囲で示すことができる。
【００２５】
図からも理解されるように、従来検知エリア６は、第一のエリア３１ａ、第二のエリア３１ｂ及び第三のエリア３１ｃを含むと共に、さらに、第二のエリア３１ｂと第三のエリア３１ｃの延長先にハッチングで示す検知エリア６ａを含む。したがって、本実施形態の検知エリア３１は、従来検知エリア６からハッチングの検知エリア６ａを除外したものということができ、この除外相当分のエリアは、透過部材２３の領域２３ｂ及び２３ｃの低透過率（Ｔｂ及びＴｃ）によるものである。
【００２６】
図５は、このような形状の検知エリア３１を有する炎検出装置２０を、実際の火災監視対象に適用した場合の図である。従来例と同様に、監視エリア３２の全体が検知エリア３１に完全に収まるように炎検出装置２０の設置位置等の調節を行うことにより、監視エリア３２の全体を漏れなく監視することができると共に、さらに、本実施形態では、以下に説明する特有の効果が得られる。
【００２７】
すなわち、本実施形態の検知エリア３１の形状、特に最遠部の形状が従来のような曲線状になっておらず、多少の凹凸があるものの、監視エリアの一般的な形状（矩形状）に沿う形状になっているため、監視エリアの外側の無用な検知エリア（図１４の符号９参照）を縮小することができる。
【００２８】
したがって、例えば、監視エリア３２の境界部分に窓のような開口部（図１５の符号１０参照）があった場合でも、この開口部を介して入り込む太陽や外灯などの外部光源からのエネルギー強度を検知レベル以下に抑えることができ、誤警報を回避できるという特有の効果が得られるのである。
【００２９】
なお、本実施形態における特徴的な事項の一つである透光部材２３の構造は、上記例示のものに限定されない。発明の意図する範囲において様々な変形例を含むことはもちろんである。以下、その好ましい変形例を列挙する。
【００３０】
図６は、第一の変形例を示す透光部材３３の平面図であり、各々の透過率をＴａ、Ｔｂ及びＴｃ（Ｔａ＞Ｔｂ＞Ｔｃ）とする三つの領域３３ａ〜３３ｃの一つ（図では領域３３ｂ）の形状を楕円形にした例である。
【００３１】
このような構造を有する透光部材３３によれば、透光部材３３の回転角度Ｆを変えることにより、検知エリア３１の形を調節することができる。例えば、監視エリアを斜めに見通すように炎検出装置２０を取り付けた場合（図９参照）に、透光部材３３の楕円形領域３３ｂの長径方向Ｅを縦にすれば、検知面の法線方向に沿って遠距離から近距離までの信号レベルを抑制することができる。
【００３２】
図７は、第二の変形例を示す透光部材３４の平面図であり、各々の透過率をＴａ、Ｔｂ及びＴｃ（Ｔａ＞Ｔｂ＞Ｔｃ）とする三種類の領域３４ａ〜３４ｃの形状を帯状にした例である。
【００３３】
このような構造を有する透光部材３４によれば、上記第一の変形例と同様に、透光部材３４の回転角度Ｆを変えることにより、検知エリア３１の形を調節することができる。
【００３４】
図８は、第三の変形例を示す透光部材３５の平面図であり、各々の透過率をＴａ、Ｔｂ及びＴｃ（Ｔａ＞Ｔｂ＞Ｔｃ）とする三つの領域３５ａ〜３５ｃの形状を帯状にしているが、透過率の高い領域３５ａと低い領域３５ｃの間に中間の透過率を持つ領域３５ｂを挟み込んで構成する点で上記第二の変形例と相違する。
【００３５】
このような構造を有する透光部材３５によれば、上記第一及び第二の変形例と同様に、透光部材３５の回転角度Ｆを変えることにより、検知エリア３１の形を調節することができるが、特に、図９に示すように、監視エリアを斜めに見通すように炎検出装置２０を取り付けた場合に、透過率の低い領域３５ｃが下になるようにすれば、検知エリア内の遠距離部分Ｅａに透過率の高い領域３５ａを対応させることができ、また、中間距離部分Ｅｂに透過率の中間の領域３５ｂを対応させることができ、さらに、近距離部分Ｅｃに透過率の低い領域３５ｃを対応させることができる。したがって、中間距離部分Ｅｂからの信号強度と近距離部分Ｅｃからの信号強度を各々の透過率に対応させて適切に抑制でき、特に、近距離部分Ｅｃからの強い信号による炎の誤検出や受信系の飽和を防止できるという特有の効果が得られる。
【００３６】
なお、上記実施形態並びに上記各変形例では、透光部材を三つ又は三種類の領域に分けているが、この領域数に限定されないことはいうまでもない。
【００３７】
例えば、図１０の第四の変形例に示す透光部材３６のように、三種類の帯状領域３６ａ〜３６ｃの中央領域３５ｃを、さらに三つの領域３５ｄ〜３５ｆに分割し、各々の領域３５ａ、３５ｂ、３５ｄ、３５ｅ、３５ｆの透過率をＴａ、Ｔｂ、Ｔｃ、Ｔｄ及びＴｅ（Ｔａ＞Ｔｂ＞Ｔｃ＞Ｔｄ＞Ｔｅ）としてもよい。
【００３８】
このような構造を有する透光部材３６によれば、特に、図９に示すように、監視エリアを斜めに見通すように炎検出装置２０を取り付けた場合に、帯状領域の長手方向を縦にすれば、検知エリア内の遠距離部分Ｅａに透過率Ｔｃの領域３５ｄを対応させることができ、また、中間距離部分Ｅｂに透過率Ｔｄの領域３５ｅを対応させることができ、さらに、近距離部分Ｅｃに透過率Ｔｅの領域３５ｆを対応させることができ、Ｔｃ＞Ｔｄ＞Ｔｅであるので、中間距離部分Ｅｂからの信号強度と近距離部分Ｅｃからの信号強度を各々の透過率に対応させて適切に抑制でき、特に、近距離部分Ｅｃからの強い信号による炎の誤検出や受信系の飽和を防止できるという上記第三の変形例と同様の効果が得られる。
【００３９】
図１１は、上記の実施形態並びに各変形例に適用して好ましい透過率調節の具体的手法を示す図である。図１１（ａ）において、３７は透光部材であり、透光部材３７は透過率Ｔａを有する、例えば、サファイアやパイレックス（登録商標）などの透光性プレート３８の裏面側（図１のケース２１の内部を臨む面）に二種類の光学波長フィルタ３９、４０を取り付けて（例えば、蒸着により）構成されている。
【００４０】
第一の光学波長フィルタ３９と第二の光学波長フィルタ４０は、図１１（ｂ）に示すように、それぞれ広波長域Ｗａと狭波長域Ｗｂの透過特性を持っており、広波長域Ｗａの透過特性を有する第一の光学波長フィルタ３９の透過光量に比べて狭波長域Ｗｂの透過特性を有する第二の光学波長フィルタ４０の透過光量は少ないから、これら二つのフィルタ３９、４０に実質的な透過率差を持たせることができる。
【００４１】
なお、透光部材の各領域毎の透過率に差を付ける方法は、かかる光学波長フィルタの利用以外にも様々考えられる。例えば、透光部材の各領域を表面荒さの異なる“すりガラス状”にしてもよい。但し、すりガラスは水滴や油等の付着によって透過率が変化するため、すりガラスの形成面を外部に露出してはならない。すなわち、炎検出装置のケースの内側にしなければならない。
【００４２】
または、本発明の課題は、上述の透光部材の構造を工夫する以外の方法でも達成可能である。例えば、多数の検知素子を二次元平面に配列するとともに、中央付近の検知素子の検知面サイズを周囲の検知素子の検知面サイズより小さくすれば、法線方向からの入射光（入射角の小さい光）に対する出力信号レベルを小さくできる一方、入射角の大きい光に対する出力信号レベルを大きくできるので、上述の透光部材の構造を工夫した場合と同等ないしは類似の効果を期待できる。
【００４３】
【発明の効果】
請求項１記載の発明によれば、透光部材を介して入射する赤外エネルギーを電気信号に変換して出力する検知素子を備えた炎検出装置において、前記透光部材に複数の領域を設け、各々の領域の前記赤外エネルギーに対する透過率に差を持たせたので、赤外エネルギーの入射角度に対応した透過率で前記電気信号のレベルを変化させることができ、監視エリアの外側の無用な検知エリアを縮小することができる。
請求項２記載の発明によれば、表面荒さの異なるすりガラス加工によって前記透過率の差を持たせたので、簡単な加工で済み、加工コストの削減を図ることができる。
請求項３記載の発明によれば、請求項２記載の発明において、すりガラス加工面を検知素子に対向する面としたので、加工面を水滴や油から保護して透過率の変動を回避できる。
請求項４記載の発明によれば、請求項１記載の発明において、透過波長帯域幅の異なる光学波長フィルタを用いて前記透過率の差を持たせたので、正確な透過率を得ることができ、検知エリアの変形精度を向上できる。
請求項５記載の発明によれば、請求項１記載の発明において、前記領域は、同心円状の複数の領域であるので、加工の容易化を図ることができる。
請求項６記載の発明によれば、請求項１記載の発明において、前記領域は、同心円状の領域と楕円状の領域を含むので、透光部材の回転角度を変えて楕円状領域の向きを変えることにより、検知エリアの形を変化させることができる。
請求項７記載の発明によれば、請求項１記載の発明において、前記領域は、帯状の領域であるりで、同心円状や楕円状の領域に比べて加工の容易化を図ることができると共に、透光部材の回転角度を変えて帯状領域の向きを変えることにより、検知エリアの形を変化させることができる。
請求項８記載の発明によれば、請求項７記載の発明において、前記帯状の領域の少なくとも一つを更に透過率の異なる複数の領域に分割するので、検知エリアの形をきめ細かく変化させることができる。
請求項９記載の発明によれば、請求項１記載の発明において、前記透光部材の中央部に位置する領域の透過率が最低、前記透光部材の周縁部に位置する領域の透過率が最大となるように設定するので、検知素子の（検知面の）法線方向の赤外エネルギーを大きく減衰でき、遠距離側の無用な検知エリアを小さくできる。
請求項１０記載の発明によれば、請求項１記載の発明において、前記透光部材の直径方向に沿って各領域の透過率が増大又は減少変化するので、透過率最低の領域を検知エリアの近距離部分に対応させれば、近距離部分からの赤外エネルギーを大きく減衰でき、近距離側の無効検知エリアを小さくできる。
請求項１１記載の発明によれば、透光部材を介して入射する赤外エネルギーを電気信号に変換して出力する検知素子を備えた炎検出装置において、前記検知素子を二次元平面に複数個配列するとともに、中央付近の検知素子の検知面サイズを周囲の検知素子の検知面サイズより小さくしたので、入射角ゼロの赤外エネルギーに対しては中央付近の検知素子によって小さな出力信号を得ることができる一方、入射角の大きい赤外エネルギーに対しては周囲の検知素子によって大きな出力信号を得ることができ、透光部材の構造を変えることなく、請求項１記載の発明と同等の効果が得られる。
【図面の簡単な説明】
【図１】炎検出装置の構成図である。
【図２】実施形態の透光部材の構造図である。
【図３】図２の透光部材を用いた場合の検知素子の信号強度を示す図である。
【図４】図２の透光部材を備えた炎検出装置の検知エリアを示す図である。
【図５】図４の検知エリアを実際の火災監視対象に適用した場合の図である。
【図６】第一の変形例に係る透光部材の構造図である。
【図７】第二の変形例に係る透光部材の構造図である。
【図８】第三の変形例に係る透光部材の構造図である。
【図９】炎検出装置を斜めに取り付けた場合の検知エリアを横方向からみた図である。
【図１０】第四の変形例に係る透光部材の構造図である。
【図１１】実施形態並びに各変形例に適用して好ましい透過率調節の具体的手法を示す図である。
【図１２】炎検出装置と被検物との関係図である。
【図１３】従来の検知エリアを示す図である。
【図１４】従来の検知エリアを実際の火災監視対象に適用した場合の図である。
【図１５】従来の検知エリアの不都合を説明する図である。
【符号の説明】
２３透光部材
２５検知素子
３３透光部材
３４透光部材
３５透光部材
３６透光部材
３７透光部材
２３ａ〜２３ｃ領域
３３ａ〜３３ｃ領域
３４ａ〜３４ｃ領域
３５ａ〜３５ｃ領域
３６ａ〜３６ｆ領域
３９、４０光学波長フィルタ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flame detection device, and more particularly, to a flame detection device that detects a flame associated with a fire using light emission of a flame.
[0002]
[Prior art]
The light emitted from the flame includes light in various wavelength regions such as visible light, ultraviolet light, and infrared light. In particular, infrared light of about 3 to 5 μm contains CO ₂ produced during combustion. It contains light in a specific wavelength range (resonance radiation near 4.3 μm) and is not easily affected by ambient light like visible light, so it has a specific band centered on this specific wavelength range. There is known a flame detection device that detects infrared energy with a sensor and determines the occurrence of a flame associated with a fire when energy of a predetermined level or higher is detected.
[0003]
Furthermore, it is also known that the light emission energy of a flame has fluctuations (hereinafter referred to as “fluctuation signal components”) centered on a low frequency band (generally about several Hz), in addition to the above-described determination of energy intensity. There is also known a flame detection apparatus that improves detection accuracy by eliminating erroneous determination due to disturbance light such as sunlight or illumination light based on frequency characteristics obtained by frequency analysis of time series signal output.
[0004]
FIG. 12 is a diagram showing the relationship between a flame detection device and an infrared energy radiator (hereinafter referred to as “test object”), wherein 1 is a sensing element provided inside the flame detection apparatus, and 2 is a test object. . The detection element 1 is, for example, a pyroelectric infrared sensor that converts infrared energy from the test object 2 that has reached the light receiving surface 1a into an electrical signal and outputs the electrical signal. Note that an optical wavelength filter for passing light in a specific wavelength region is attached to the front surface of the light receiving surface 1a, but is omitted in the drawing.
[0005]
The output signal level of the detection element 1 depends on the distance R between the detection element 1 and the test object 2 and the incident angle θ of the infrared energy to the light receiving surface (θ is the normal 3 of the light receiving surface of the detection element 1). Depending on the angle). For example, the output signal level decreases as R increases, and the output signal level decreases as θ increases.
[0006]
Now, while making the test object 2 a specified flame model, plotting the output signal level of the sensing element 1 on a plan view while changing R and θ in various ways, the minimum output signal level that can detect the flame By connecting the plot points, the detection area of the flame detection device can be grasped.
[0007]
FIG. 13 is a diagram illustrating a detection area. In the figure, 4 is a flame detection device, 5 is a normal line of a light receiving surface (not shown), and 6 is a line connecting plot points of the minimum output signal level at which flame can be detected. An area (hereinafter, line 6 is referred to as a detection area). However, in the drawing, an invalid area (an area where the output signal level is too large and accurate flame detection cannot be performed) near the flame detection device 4 is omitted.
[0008]
The detection area 6 extends in a fan shape from the light receiving point P of the flame detection device 4 (detection element thereof) and is closed by drawing a curve at the tip of the detection area 6. The length L of the straight line connecting the lines corresponds to the distance R corresponding to the minimum output signal level at which a flame can be detected. An angle φ formed by a straight line connecting the arbitrary point x on the curve with the light receiving point P and the normal 5 corresponds to the incident angle θ corresponding to the minimum output signal level at which flame can be detected.
[0009]
In the detection area 6 shown in the figure, the maximum point of the distance R at which the flame can be detected is at a point y on the normal 4 where θ is minimum (θ = 0). That is, the portion farthest from the light receiving point P in the detection area 6 is in the vicinity of the point y.
[0010]
When the flame detection device 4 having the detection area 6 having such a shape is applied to an actual fire monitoring target, the flame is set so that the entire monitoring area 8 is completely contained in the detection area 6 as shown in FIG. The installation position of the detection device 4 is adjusted. Thereby, the whole monitoring area 8 can be monitored without omission.
[0011]
[Problems to be solved by the invention]
However, in the conventional flame detection device, the shape of the detection area 6, particularly the shape of the farthest part, is curved, so it does not match the general shape (rectangular shape) of the monitoring area, An unnecessary detection area 9 spread outside the monitoring area 8.
[0012]
For this reason, for example, as shown in FIG. 15, when there is an opening 10 like a window at the boundary portion of the monitoring area 8, light from the external light source 11 such as the sun or an external light enters through the opening 10, As a result of light reception by the flame detection device 4, there is a problem that a false alarm may be issued.
[0013]
Accordingly, the problem to be solved by the present invention is to reduce the useless detection area outside the target monitoring area by changing the shape of the detection area.
[0014]
[Means for Solving the Problems]
The invention according to claim 1 is a flame detection device for detecting a fire in a monitoring area, comprising a detection element that converts infrared energy incident through a light transmissive member into an electric signal and outputs the electric signal. A plurality of regions, and the transmittance corresponding to the infrared energy of each region of the translucent member so that the detection area of the detection element completely includes the monitoring region and the detection area follows the shape of the monitoring region It is characterized by having a difference.
The invention described in claim 2 is characterized in that, in the invention described in claim 1, the difference in transmittance is given by ground glass processing with different surface roughness.
According to a third aspect of the present invention, in the second aspect of the present invention, the ground glass processed surface is a surface facing the detection element.
According to a fourth aspect of the present invention, in the first aspect of the present invention, the difference in transmittance is provided by using optical wavelength filters having different transmission wavelength bandwidths.
According to a fifth aspect of the invention, in the first aspect of the invention, the region is a plurality of concentric regions.
According to a sixth aspect of the invention, in the first aspect of the invention, the region includes a concentric region and an elliptical region.
The invention according to claim 7 is the invention according to claim 1, wherein the region is a band-like region.
The invention according to claim 8 is the invention according to claim 7, characterized in that at least one of the band-like regions is further divided into a plurality of regions having different transmittances.
According to a ninth aspect of the present invention, in the first aspect of the present invention, the transmittance of the region located in the central portion of the translucent member is the lowest, and the transmittance of the region located in the peripheral portion of the translucent member is the largest. It sets so that it may become.
According to a tenth aspect of the present invention, in the first aspect of the present invention, the transmittance of each region increases or decreases along the diameter direction of the translucent member.
The invention according to claim 11 is a flame detection apparatus for detecting a fire in a monitoring area, comprising a detection element that converts infrared energy incident through a translucent member into an electrical signal and outputs the electrical signal. A plurality of two-dimensional planes are arranged , and the detection surface size of the detection element near the center is detected so that the detection area of the flame detection device completely includes the monitoring area and the detection area follows the shape of the monitoring area. and wherein the smaller than the detection surface size of the element Kusuru.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 is a structural diagram of a flame detection apparatus. The flame detection device 20 includes a thin cylindrical case 21 and a sensor package 22 housed in the case 21. The flame detection device 20 is externally connected through a translucent member 23 fitted into one end surface of the case 21. Infrared energy is captured, signal light in a specific wavelength range filtered by the optical wavelength filter 24 of the sensor package 22 is received by the sensing element 25, converted into an electrical signal, and output to a flame detection unit (not shown).
[0017]
The optical wavelength filter 24 has, for example, transmission characteristics in a wavelength band including a wavelength region near 4.3 μm called CO ₂ resonance radiation generated during combustion, and the detection element 25 has, for example, Although it is a pyroelectric infrared sensor, it is not limited to this. In short, what is necessary is just to have a detection characteristic necessary for a flame detection device that detects the flame associated with a fire using the light emission of the flame.
[0018]
The detection viewing angle θT of the illustrated flame detection device 20 is an opening angle of lines 26 and 27 connecting the end of the light receiving surface (the surface facing the optical wavelength filter 24) of the detection element 25 and the end of the translucent member 23. This angle θT corresponds to an angle extending in a fan shape from the light receiving point P of the flame detection device 4 (detection element thereof) in the detection area 6 of FIG.
[0019]
The characteristic matters of the present embodiment are exclusively in the structure of the translucent member 23. That is, one role of the translucent member 23 is to protect the sensor package 22 from raindrops, dust, and the like integrated with the case 21, as in the translucent member of the prior art. Further, it differs from the prior art in that it has a dual role of providing different transmittances according to the incident angle for incident light within the range of the detection viewing angle θT.
[0020]
FIG. 2 is a plan view of the translucent member 23 of the present embodiment. In the illustrated example, the thin plate-like light transmitting member 23 formed in a substantially circular shape has three concentric circular regions 23a, 23b, and 23c. When the transmittance of each region is Ta, Tb, and Tc, Ta >Tb> Tc. However, Ta is almost 100% or as close to 100% as possible. Here, the transmittance refers to a ratio (generally expressed in%) of a transmitted wave to an incident wave when a wave is transmitted through a material layer or an interface between two different media. For example, when the transmittance is 100%, the intensity of the incident wave is equal to the intensity of the transmitted wave (the transmission loss is zero), and when the transmittance is 0%, all of the incident wave is lost during transmission. The intensity of the transmitted wave becomes zero.
[0021]
FIG. 3 is a diagram illustrating the signal intensity of the detection element 25 when the translucent member 23 of FIG. 2 is used. The fan-shaped figures 30a to 30c represent signals corresponding to the regions 23a to 23c of the translucent member 23, and the signal intensity is schematically represented by the length from the root of the fan to the tip. That is, since Ta>Tb> Tc, the transmitted wave intensity of the region 23a having the transmittance Ta is maximized, and the transmitted wave intensity of the region 23b having the transmittance Tb is next to the transmission of the region 23c having the transmittance Tc. Wave intensity is minimized.
[0022]
The difference between the lengths of the three types of fan-shaped figures 30a to 30c corresponds to the difference in transmittance between the regions 23a to 23c of the translucent member 23. For example, Ta = 90%, Tb = 60%, Tc = 30% Then, since the transmittance difference of each of Ta, Tb, and Tc is 30%, if the light receiving characteristics of the detection element 25 are ignored, the difference in length between the three types of fan-shaped figures 30a to 30c is 30%. It will be considerable.
[0023]
FIG. 4 is a diagram illustrating a detection area 31 of the flame detection device 20 including the light transmissive member 23 described above. The illustrated detection area 31 is a combination of three types of areas 31a to 31c. The first area 31a corresponds to the fan-shaped figure 30a, the second area 31b corresponds to the fan-shaped figure 30b, The third area 31c corresponds to the fan-shaped figure 30c.
[0024]
Now, if the transmittance Ta of the region 23a of the translucent member 23 is the same value as the transmissivity of the conventional translucent member, the detection area 6 of the conventional flame detection device (hereinafter referred to as “conventional detection area”) is a broken line. Can be shown by range.
[0025]
As can be understood from the drawing, the conventional detection area 6 includes a first area 31a, a second area 31b, and a third area 31c, and further includes a second area 31b and a third area 31c. The extension area includes a detection area 6a indicated by hatching. Therefore, it can be said that the detection area 31 of the present embodiment excludes the hatching detection area 6a from the conventional detection area 6, and the area corresponding to the exclusion corresponds to the low transmittance of the regions 23b and 23c of the transmission member 23. (Tb and Tc).
[0026]
FIG. 5 is a diagram when the flame detection apparatus 20 having the detection area 31 having such a shape is applied to an actual fire monitoring target. As in the conventional example, the entire monitoring area 32 can be monitored without omission by adjusting the installation position of the flame detection device 20 so that the entire monitoring area 32 is completely within the detection area 31. Furthermore, in this embodiment, the following specific effects can be obtained.
[0027]
In other words, the shape of the detection area 31 of the present embodiment, particularly the shape of the farthest part, is not curved as in the prior art, and there are some irregularities, but the general shape (rectangular shape) of the monitoring area. Since it has a shape along, it is possible to reduce an unnecessary detection area (see reference numeral 9 in FIG. 14) outside the monitoring area.
[0028]
Therefore, for example, even when there is an opening like a window (see reference numeral 10 in FIG. 15) at the boundary portion of the monitoring area 32, the energy intensity from the external light source such as the sun and outside light entering through this opening is reduced. It can be suppressed below the detection level, and a unique effect that a false alarm can be avoided is obtained.
[0029]
In addition, the structure of the translucent member 23 which is one of the characteristic matters in the present embodiment is not limited to the above-described example. It goes without saying that various modifications are included within the intended scope of the invention. Hereinafter, preferable modifications thereof will be listed.
[0030]
FIG. 6 is a plan view of the translucent member 33 showing a first modified example, and is one of three regions 33a to 33c (Ta>Tb> Tc) (Ta>Tb> Tc). In the figure, the area 33b) is an ellipse.
[0031]
According to the translucent member 33 having such a structure, the shape of the detection area 31 can be adjusted by changing the rotation angle F of the translucent member 33. For example, when the flame detection device 20 is attached so as to look obliquely through the monitoring area (see FIG. 9), if the major axis direction E of the elliptical region 33b of the translucent member 33 is vertical, the normal direction of the detection surface The signal level from a long distance to a short distance along the line can be suppressed.
[0032]
FIG. 7 is a plan view of a translucent member 34 showing a second modification, and the shapes of three types of regions 34a to 34c with the respective transmittances being Ta, Tb, and Tc (Ta>Tb> Tc) are shown. This is an example of a strip.
[0033]
According to the translucent member 34 having such a structure, the shape of the detection area 31 can be adjusted by changing the rotation angle F of the translucent member 34 as in the first modification.
[0034]
FIG. 8 is a plan view of the translucent member 35 showing a third modification, and the shapes of the three regions 35a to 35c having respective transmittances of Ta, Tb and Tc (Ta>Tb> Tc) are belt-like. However, the second modified example is different from the second modified example in that a region 35b having an intermediate transmittance is sandwiched between a region 35a having a high transmittance and a region 35c having a low transmittance.
[0035]
According to the translucent member 35 having such a structure, the shape of the detection area 31 can be adjusted by changing the rotation angle F of the translucent member 35 as in the first and second modifications. In particular, as shown in FIG. 9, when the flame detection device 20 is mounted so as to look obliquely through the monitoring area, if the low-transmittance region 35c is positioned below, A region 35a having a high transmittance can be associated with the distance portion Ea, a region 35b having a medium transmittance can be associated with the intermediate distance portion Eb, and a region having a low transmittance can be associated with the short distance portion Ec. 35c can be made to correspond. Accordingly, the signal intensity from the intermediate distance portion Eb and the signal intensity from the short distance portion Ec can be appropriately suppressed in correspondence with the respective transmittances, and in particular, erroneous detection or reception of flames due to a strong signal from the short distance portion Ec. A unique effect is obtained in that saturation of the system can be prevented.
[0036]
In addition, in the said embodiment and said each modification, although the translucent member is divided into three or three types of area | regions, it cannot be overemphasized that it is not limited to this number of area | regions.
[0037]
For example, like the translucent member 36 shown in the fourth modified example of FIG. 10, the central region 35c of the three types of belt-like regions 36a to 36c is further divided into three regions 35d to 35f, and each region 35a, The transmittances of 35b, 35d, 35e, and 35f may be Ta, Tb, Tc, Td, and Te (Ta>Tb>Tc>Td> Te).
[0038]
According to the translucent member 36 having such a structure, as shown in FIG. 9, when the flame detection device 20 is mounted so as to look obliquely at the monitoring area, the longitudinal direction of the belt-like region is vertically set. For example, the region 35d having the transmittance Tc can be associated with the long-distance portion Ea in the detection area, and the region 35e having the transmittance Td can be associated with the intermediate-distance portion Eb. Since the region 35f of the transmittance Te can be made to correspond to Tc>Td> Te, the signal intensity from the intermediate distance portion Eb and the signal strength from the short distance portion Ec are appropriately matched to each transmittance. In particular, it is possible to obtain the same effect as that of the third modified example in which it is possible to prevent erroneous detection of flames due to a strong signal from the short distance portion Ec and saturation of the receiving system.
[0039]
FIG. 11 is a diagram showing a specific method for adjusting the transmittance that is preferably applied to the above-described embodiment and each modification. In FIG. 11A, 37 is a translucent member, and the translucent member 37 has a transmissivity Ta, for example, the back side of a translucent plate 38 such as sapphire or Pyrex (registered trademark) (the case of FIG. 1). Two types of optical wavelength filters 39, 40 are attached (for example, by vapor deposition) to the surface facing the inside of the member 21.
[0040]
As shown in FIG. 11B, the first optical wavelength filter 39 and the second optical wavelength filter 40 have transmission characteristics in a wide wavelength range Wa and a narrow wavelength range Wb, respectively. Since the amount of transmitted light of the second optical wavelength filter 40 having the transmission characteristics in the narrow wavelength region Wb is smaller than the amount of transmitted light of the first optical wavelength filter 39 having the transmission characteristics, the two filters 39 and 40 have substantially no transmission light. It is possible to have a difference in transmittance.
[0041]
Various methods other than the use of the optical wavelength filter are conceivable as a method of giving a difference in the transmittance of each region of the light transmitting member. For example, each region of the translucent member may be made of “frosted glass” having different surface roughness. However, since the transmittance of ground glass changes due to adhesion of water droplets or oil, the ground glass forming surface must not be exposed to the outside. That is, it must be inside the case of the flame detector.
[0042]
Alternatively, the object of the present invention can be achieved by a method other than devising the structure of the above-described translucent member. For example, if a large number of detection elements are arranged in a two-dimensional plane and the detection surface size of the detection elements near the center is smaller than the detection surface size of the surrounding detection elements, incident light from the normal direction (with a small incident angle) The output signal level with respect to light with a large incident angle can be increased while the output signal level with respect to light) can be reduced, so that the same or similar effect as that obtained when the structure of the above-described translucent member is devised can be expected.
[0043]
【The invention's effect】
According to the first aspect of the present invention, in the flame detection apparatus including a detection element that converts infrared energy incident through the light transmitting member into an electrical signal and outputs the electric signal, the light transmitting member is provided with a plurality of regions. Since each region has a difference in transmittance with respect to the infrared energy, the level of the electrical signal can be changed at a transmittance corresponding to the incident angle of the infrared energy, and the outside of the monitoring area is useless. The detection area can be reduced.
According to the second aspect of the present invention, since the difference in transmittance is given by ground glass processing with different surface roughness, simple processing is sufficient, and processing cost can be reduced.
According to the invention described in claim 3, in the invention described in claim 2, since the ground glass processed surface is a surface opposed to the detection element, the processed surface can be protected from water droplets or oil and fluctuations in transmittance can be avoided.
According to the invention described in claim 4, in the invention described in claim 1, since the difference in transmittance is provided by using optical wavelength filters having different transmission wavelength bandwidths, an accurate transmittance can be obtained. The deformation accuracy of the detection area can be improved.
According to the invention described in claim 5, in the invention described in claim 1, since the region is a plurality of concentric regions, the processing can be facilitated.
According to the invention of claim 6, in the invention of claim 1, the region includes a concentric circular region and an elliptical region. By changing, the shape of the detection area can be changed.
According to a seventh aspect of the invention, in the first aspect of the invention, the region is a band-like region, and the processing can be facilitated as compared with a concentric or elliptical region. The shape of the detection area can be changed by changing the rotation angle of the translucent member to change the direction of the belt-like region.
According to the invention described in claim 8, in the invention described in claim 7, since at least one of the band-like regions is further divided into a plurality of regions having different transmittances, the shape of the detection area can be finely changed. it can.
According to the ninth aspect of the present invention, in the first aspect of the present invention, the transmittance of the region located in the central portion of the translucent member is the lowest, and the transmissivity of the region located in the peripheral portion of the translucent member is low. Since it is set to be maximum, the infrared energy in the normal direction (of the detection surface) of the detection element can be greatly attenuated, and the useless detection area on the far side can be reduced.
According to the invention described in claim 10, in the invention described in claim 1, since the transmittance of each region increases or decreases along the diameter direction of the translucent member, the region having the lowest transmittance is detected in the detection area. If it corresponds to the short distance portion, the infrared energy from the short distance portion can be greatly attenuated, and the invalid detection area on the short distance side can be reduced.
According to the eleventh aspect of the present invention, in the flame detection apparatus including a detection element that converts infrared energy incident through the light-transmitting member into an electrical signal and outputs the electrical signal, a plurality of the detection elements are arranged in a two-dimensional plane. Since the detection surface size of the detection elements near the center is smaller than the detection surface size of the surrounding detection elements, a small output signal can be obtained by the detection elements near the center for infrared energy with a zero incident angle. On the other hand, for infrared energy having a large incident angle, a large output signal can be obtained by the surrounding sensing element, and the same effect as that of the invention according to claim 1 can be obtained without changing the structure of the translucent member. can get.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a flame detection device.
FIG. 2 is a structural diagram of a translucent member of the embodiment.
FIG. 3 is a diagram illustrating signal intensity of a sensing element when the light-transmissive member of FIG. 2 is used.
4 is a diagram showing a detection area of a flame detection device provided with the translucent member of FIG. 2;
FIG. 5 is a diagram when the detection area of FIG. 4 is applied to an actual fire monitoring target.
FIG. 6 is a structural diagram of a translucent member according to a first modification.
FIG. 7 is a structural diagram of a translucent member according to a second modification.
FIG. 8 is a structural diagram of a translucent member according to a third modification.
FIG. 9 is a view of the detection area when the flame detection device is attached obliquely as seen from the side.
FIG. 10 is a structural diagram of a translucent member according to a fourth modification.
FIG. 11 is a diagram showing a specific method for adjusting the transmittance that is preferably applied to the embodiment and each modification.
FIG. 12 is a relationship diagram between a flame detection device and a test object.
FIG. 13 is a diagram showing a conventional detection area.
FIG. 14 is a diagram when a conventional detection area is applied to an actual fire monitoring target.
FIG. 15 is a diagram for explaining disadvantages of a conventional detection area.
[Explanation of symbols]
23 translucent member 25 sensing element 33 translucent member 34 translucent member 35 translucent member 36 translucent member 37 translucent member 23a-23c region 33a-33c region 34a-34c region 35a-35c region 36a-36f region 39, 40 Optical wavelength filter

Claims

In a flame detection device for detecting a fire in a monitoring area, comprising a detection element that converts infrared energy incident through a light transmitting member into an electrical signal and outputs the electrical signal,
A plurality of areas are provided in the translucent member, and the infrared energy of each area of the translucent member is adjusted so that the detection area of the detection element completely includes the monitoring area and the detection area follows the shape of the monitoring area. A flame detection device characterized by having a difference in corresponding transmittance.

The flame detection apparatus according to claim 1, wherein the difference in transmittance is provided by ground glass processing with different surface roughness.

The flame detection device according to claim 2, wherein the ground glass processed surface is a surface facing the detection element.

2. The flame detection apparatus according to claim 1, wherein the difference in transmittance is provided by using optical wavelength filters having different transmission wavelength bandwidths.

The flame detection device according to claim 1, wherein the region is a plurality of concentric regions.

The flame detection device according to claim 1, wherein the region includes a concentric circular region and an elliptical region.

The flame detection device according to claim 1, wherein the region is a belt-like region.

The flame detection device according to claim 7, wherein at least one of the band-like regions is further divided into a plurality of regions having different transmittances.

2. The flame according to claim 1, wherein the transmittance is set so that the transmittance of the region located in the central portion of the translucent member is lowest and the transmittance of the region located in the peripheral portion of the translucent member is maximized. Detection device.

The flame detection apparatus according to claim 1, wherein the transmittance of each region increases or decreases along the diameter direction of the translucent member.

In a flame detection device for detecting a fire in a monitoring area, comprising a detection element that converts infrared energy incident through a light transmitting member into an electrical signal and outputs the electrical signal,
A plurality of detection elements are arranged in a two-dimensional plane, and the detection surface size of the detection elements near the center is such that the detection area of the flame detection device completely includes the monitoring area and the detection area follows the shape of the monitoring area. flame detection device, characterized in that the smaller than the detection surface size of the surrounding detector elements Kusuru.